Piperazinium Hexachlorodicuprate (PHCC) is shown to be a frustrated quasi-two-dimensional quantum Heisenberg antiferromagnet with a gapped spectrum. Zero-field inelastic neutron scattering and susceptibility and specific heat measurements as a function of applied magnetic field are presented. At T = 1.5 K, the magnetic excitation spectrum is dominated by a single propagating mode with a gap, Delta = 1 meV, and bandwidth of approximately 1.8 meV in the (h0l) plane. The mode has no dispersion along the b* direction indicating that neighboring a-c planes of the triclinic structure are magnetically decoupled. The heat capacity shows a reduction of the gap as a function of applied magnetic field in agreement with a singlet-triplet excitation spectrum. A field-induced ordered phase is observed in heat capacity and magnetic susceptibility measurements for magnetic fields greater than H_c1 approximately equal to 7.5 Tesla. Analysis of the neutron scattering data reveals the important exchange interactions and indicates that some of these are highly frustrated.
Cite
@article{arxiv.cond-mat/0104150,
title = {Frustration-Induced Two Dimensional Quantum Disordered Phase in Piperazinium Hexachlorodicuprate},
author = {M. B. Stone and I. Zaliznyak and Daniel H. Reich and C. Broholm},
journal= {arXiv preprint arXiv:cond-mat/0104150},
year = {2009}
}
Comments
13 pages with 14 figures, 7 pages of text, 6 pages of figures. Submitted to Phys. Rev. B 4/7/2001. email comments to dhr@pha.jhu.edu or mstone@pha.jhu.edu